Type Synthesis And Kinematics Analysis Of Umbrella-shaped Deployable Mechanisms Based On Two-layer And Two-loop Spatial Linkages

Deployable mechanisms are the core framework of many major high-end equipments,such as large space folding antennas,communication satellite platforms,space extension arms and space solar arrays.With the rapid development of space activities in our country,the demand for deployable mechanisms with characteristics of large-scale,high-precision,high-rigidity,high-stability and lightweight has been becoming more and more urgent.The umbrella-liked shape is one of the most classic shapes of deployable mechanisms,which is widely used in space equipment.Therefore,the innovative design of umbrella-shaped deployable mechanism is of great significance to promote the development of space deployable equipment in our country.But the traditional umbrella-shaped deployable mechanisms mainly concentrated on rib support linkages with lower rigidity.So far,there are relatively few spatial closed-loop deployable linkage units that can be used to construct high-stiffness umbrella-shaped deployable mechanisms.Based on this,in this paper,a new family of umbrella-shaped deployable mechanisms based on the two-layer and two-loop spatial linkages is proposed,which is deeply researched in the aspects of type synthesis of the units,mobile assembly modes between the deployable units and kinematics analysis of the deployable mechanisms.The details are as follows:Firstly,according to the requirement of single degree of freedom,the two-layer and two-loop spatial linkages with coupling chains is divided into five categories.And on the basis of analyzing the characteristics of the existing umbrella-shaped developable mechanisms,the mechanism characteristics of the two-layer and two-loop spatial linkages used as deployable element are defined.Then,the five types of two-layer and two-loop spatial deployable units are synthesized separately.In this process,each kind of deployable units can be divided into different structural forms according to the position of the coupling chains.Based on structural forms,a concise and efficient method is proposed for synthesizing two-layer and two-loop spatial linkage units based on modular combinations,and a variety of two-layer and two-loop spatial deployable units are obtained.In addition,mobile assembly modes of the deployable units are studied.Umbrellashaped deployable mechanism is usually constructed by several deployable units according to mobile assembly mode,so after completing the type synthesis of deployable units,the mobile assembly modes between units are established according to the requirements of single degree of freedom and structural symmetry of the mechanism.There are three mobile assembly modes that can be applied to deployable units of different structural forms.Then,umbrella-shaped deployable mechanisms are constructed based on the developed deployable units and the established mobile assembly modes.Finally,the kinematics of the deployable units is analyzed.The method of forward kinematic position solution for deployable units is established by using D-H parameter method and combining the characteristics of deployable units.Moreover,by summarizing the common points among different deployable units,a unified method for inverse kinematics position solution of deployable mechanisms is established on the basis of analyzing the geometric relationship between the rotating pair and link of deployable units,and some simulation experiments have been done.Based on the analysis of kinematics position,the kinematics velocity analysis of deployable mechanisms is completed with Jacobian Matrix constructed by vector product method.In conclusion,in this thesis,a new family of umbrella-shaped deployable mechanisms based on the two-layer and two-loop spatial linkages is proposed and its kinematics is studied,which breaks through the bottleneck of innovative design of umbrella-shaped deployable mechanisms.,and provides a theoretical basis and reference for researchers engaged in the research of umbrella-shaped deployable antenna mechanism.